Construction method of large-span asymmetrical double-arch railway tunnel under terrain bias pressure condition

The invention provides a construction method of a large-span asymmetrical double-arch railway tunnel under a terrain bias pressure condition. The method is used for greatly shortening construction period and improving construction efficiency by simplifying construction steps. In the construction method, a middle pilot tunnel, an inside tunnel chamber and an outside tunnel chamber are sequentiallyexcavated, and unbalanced support systems are adopted in the inside tunnel chamber and the outside tunnel chamber, which effectively controls deformation of the top part of a middle partition wall and arch parts of the big main tunnel chamber and the small main tunnel chamber as well as side walls (the maximum deformation is controlled within 20mm), greatly shortens construction period, simplifies construction steps, improves construction efficiency by 30%, and the problem of water leakage on the top part of the middle partition wall is effectively solved.